Radio tuning and indicating apparatus



1936. E. F. MCDONALD. JR 2,052,233

RADIO TUNING AND INDICATING APPARATUS Filed Sept. 1, 1934 2 Sheets-Sheetl .ZZzv/entofl V 'BI QMFMJDOW Aug. 25, 1936.

E. F. M DONALD JR 2,052,238 RADIO TUNING AND INDICATING APPARATUS FiledSept. 1, 1934 2 Sheets-Sheet 2 W I" .3 W V fiuxwzion' @QRQMDOYZQMfiPatented Aug. 25, 1936 UNITED STATES PATENT OFFICE RADIO TUNING ANDINDICATING APPARATUS Eugene F. McDonald, Jr., Chicago, 111., assignor toZenith Radio Corporation, Chicago, IlL, a

corporation of Illino Application September 1, 1934, Serial No. 742,470

3 Claims.

marks upon the tuning scale to determine such positioning. Finecalibrations of tuning scales are difficult to read,and whilethis haslong been recognized as obtaining in the accurate adjustment of theradio tuning elements of the more selective types of broadcast-bandreceivers, and has always been an objectionable feature in the tuning ofshort-wave receivers, the advent of the so-called all-wave receiver hasaccentuated the need of tuning and indicating apparatus through whichthe careful positioning of the tuningelements may be both quickly andaccurately effected and definitely and accurately determined.

In such all-wave receivers, in which the tuning range extends over andbetween the short-wave and the broadcast bands, and in which a singleset of adjustable tuning elements is used to cover this greatly extendedrange, the exact positioning of the tuning elements is absolutelynecessary throughout the shorter wave-bands, and the tuning andindicating apparatus should be such as will permit the operator to bothobtain and ob serve extremely accurate and delicate adjustments and alsoenable him to obtain such adjustments as quickly as he has beenaccustomed to do when tuning for broadcast band reception.

It is impracticable to employ a continuous graduated tuning scale whichwill embrace the full tuning range of an all-wave receiver, and it isthe common practice to break up the scale into sections, such as I haveillustrated upon the dial shown in Figure l, leaving that portioncovering the broadcast band substantially as it has beenthat is to say,with ten-kilocycle calibrations, but, in using the arrangements so farprovided in allwave receivers the result has been to add to theconfusion of the operator in definitely determining the proper positionsofthe tuning elements for short-wave reception, and I have added agraduated circular scale, spread circumferentially upon the dial so thatthe graduations thereof may be easily and conveniently observed, and acorresponding pointer'to indicate in connection therewith fractionaladjustments of the tuning elements between the graduation marks of eachand all of the several tuning scales.

The principal radio apparatus.

Another object of my invention is to provide 10 an arrangement throughwhich such accurate and delicate adjustment may be obtained simply andquickly, so that, while the apparatus is parproviding for 15 tuningelements throughout the possible confusion of the operator will beminimized; and so that he will not find it necessary to depend uponhearing the desired signal to determine if he has properly adjusted thetuning elements to receive it.

These and other objects and advantages of my invention will appear inthe following description.

In the drawings- Figure l is a front elevational view, showing theoperating knob and the indicating devices forming a part of myinvention;

Fig. 2 is a vertical sectional view, taken upon the line 2-2 of Fig. 1,showing the complete operating mechanism embodying my invention; 40 andFig. 3 is an enlarged fragmentary sectional view, illustrating in detailthe construction and arrangement of some of the parts shown in Fig. 2.

Referring to Fig. 2, I have shown a conven- 45 tional form of variablecondenser having statorplates i and rotor-plates 2, the latter beingfixed upon the rotatable condenser-shaft 3, and the entire condenserstructure being secured in any desirable manner upon the fixed support4. Condenser-shaft 3 is centrally bored at its forward end-part, andinto this boring 5 is tightly pressed the rearward end-Dart of thearbor-shaft 6, the arbor-shaft thus forming a forward extension of saidcondenser-shaft, and this method of attach- 55 ment being one whichaffords accurate alinement and secure attachment of my device withshafts of various types of variable condensers.

Shaft 1 is rotatably supported in bearings 8 and 9 and p'ojectsforwardly through the instrument panel l0, adjusting knob ll beingremovably fixed upon the outwardly presented end-part. Afriction-drive-wheel I2 is fixed upon shaft 1 and is formed by tworim-flared disks l3 and i4 tightly pressed together (Fig. 3) upon a hubl5. These disk's I3 and i4 bear upon the opposite circumferential edgesof a relatively larger drive-disc l6 of celluloid, pyralin, or othersuitable material, the central mounting-plate ll of which drive-disc isremovably fixed upon condenser-shaft 3 by means of set-screw I8. Theabove described mechanism constitutes a frictiondrive vernier adjustingmeans, by which the operator may quickly and accurately adjust therotor-plates 2 of the variable condenser. This particular constructionof the vernier adjusting means does not form a part of this invention,however, and any other construction of this part of my device may beused, if desired, and the r turning ratio of the shaft 1 with respect tothe condenser-shaft 3 may be changed without departing from the spiritand scope of my invention.

A double-ended pointer I9 is fixed upon the forward end-part of a sleeve20 which extends rearwardly through a central aperture in theindicator-dial 2| and is snugly fitted in frictional engagement over themajor part of arbor-shaft 6, the frictional engagement being such as toinsure the turning of the pointer 19 by the condensershaft 3 and yetpermit it to be adjustably positioned in the testing of the assembledapparatus to accurately indicate upon the dial 2| the various tuningpositions of the rotor-plates 2. The double-ended pointer l9 co-operateswith a plurality of tuning scales, A, B, C, D and E (Fig. 1),

some of which are calibrated to indicate megacycles for short-wavetuning, and one of which E, is calibrated to indicate kilocycles forbroadcast-band tuning. I have not shown the usual tuning coils and thecircuit connections therefor, since neither their construction norarrangement is involved herein, and I do not wish my invention to beconsidered as limited in any respect to the use of the scale arrangementI have shown for illustrative purposes upon the indicator-dial 2|.Different scales and different arrangements of scales may be employed asoccasion may require or as may e preferred.

A second pointer 22 is fixed upon the forward end-part of a sleeve 23which is fitted to turn freely upon sleeve 20 and extends rearwardlytherewith through the'central aperture in the indicator-dial 2i andthrough bearing-plates 24 and 25. Sleeve 23 carries a pinion-gear 26fixed tightly thereupon between bearing-plates 24 and 25 and in meshwith a gear-wheel 21. Gearwheel 21 is fixed upon a counter-shaft 28which is supported in bearing-plates 24 and 25 and carries a pinion-gear29 tightly fixed thereupon at or near its rearward end-part. Pinion-gear29 meshes with a gear-wheel 30 tightly fixed upon arbor-.shaft 6. Acover 3| of glass or other transparent material is positioned over theindicator-dial 2| and pointers l9 and 22 to permit observance thereofand to prevent tampering with their proper adjustment.

The ratio of movement of the various parts is.

such that a single turn of the adjusting knob H will effect a partialrotation or Vernier adjustment of the condenser-shaft 3 and pointer l9,and at the same time effect'more than one revolution of pointer 22. Itwill be observed that pointer 22 traverses a graduated scale 32, thecalibration of which is easy to read, and that the relative positions ofthe two pointers l9 and 22 are as convenient for observation as the hourand minute hands of a timepiece.

The operation of the device is simple. It consists in the turning of theadjusting knob ll until the double-ended pointer 19 indicates upon theproper scale the approximate tuning position desired, this adjustmentbeing obtainable quickly, the more accurate and delicate adjustment ofthe tuning devices being had by observing the position of the pointer 22with relation to the scale 32.

I claim- 1. In apparatus of the character described, the combination ofa dial having a plurality of concentrically arranged sets of arcuatescales and a circular scale displayed thereupon, a plurality of pointersarranged to turn upon a common axis, one of said pointers beingdouble-ended with its diametrically opposite end-parts registering withdifferent scales of said sets of arcuate scales and a second of saidpointers registering with said circular scale, driving means,speed-reducing transmission means connecting said driving means withsaid one of said pointers, and speedincreasing transmission meansconnecting said one of said pointers with said second of said pointers.

2. In apparatus of the character described, the combination of a dialhaving a plurality of differently graduated semi-circular scales and anevenly graduated circular scale displayed thereupon, said plurality ofscales being concentrically arranged and representing different tuningwavebands andsaid circular scale surrounding said plurality of scalesand representing fractional adjustments only, a plurality of pointers ofdifferent length arranged to turn upon a common axis, one of saidpointers registering with said plurality of scales and a second andlonger one of said pointers registering with said circular scale, anddriving means connected with said pointers to effect their simultaneousoperation at relatively different speeds.

3. The combination, of an adjustable radio tuning element, a drivingshaft, and transmission means connecting said shafts whereby onerevolution of said driving shaft will effect a partial revolution ofsaid rotatable shaft, of a dial having a plurality of differentlygraduated semi-circular scales and an evenly graduated circular scaledisplayed thereupon, said plurality of scales being concentricallyarranged and representing difierent tuning wavebands and said circularscale surrounding said plurality of scales and representing fractionaladjustments only, a plurality of pointers of different length arrangedto turn upona common axis, one of said pointers registering with saidplurality of scales and a second and longer one of said pointersregistering with said circular scale, and transmission means connectingsaid pointers with each other and with said rotatable shaft whereby theoperation of said driving shaft will effect the simultaneous movement ofsaid pointers at relatively different speeds.

EUGENE F. MCDONALD, JR.

with the rotatable shaft

